Electronic method and system for detection of conducting or dielectric medium with dielectric constant higher than that of air

ABSTRACT

The method of detecting the presence of a conducting or dielectric environment with dielectric constant higher than that of air, of this invention, consists in counting the number of control signals (No), resulting from the relationship No=f(Qp, Qod, Ucc, Up, T), sent from the control system (US) as necessary to charge the capacitor (Cp) and then to discharge the previously-charged capacitor (Cp) to a threshold voltage (Up) preset by the control system (US), with the subsequent counting of the number of control signals (Nx), resulting from the relationship Nx=f(Qp, Qx, Ucc, Up, T), sent from said control system (US) as necessary to charge the capacitor (Cx), and then the previously-charged capacitor (Cp) is discharged to said threshold voltage (Up) preset by said control system (US) and the quantities of determined control signals (Nx) are compared with the reference state and the obtained difference in those signals indicates the presence of a conductive or dielectric environment in the immediate environment of the capacitor (Cx).

The subject of this invention is the electronic method and system fordetection of conducting or dielectric environment with dielectricconstant higher than that of air, applicable in particular forcontinuous contactless electronic monitoring of the level of liquidfoodstuffs and other liquids in containers.

The prior-art methods of gauging liquid levels in containers consist inintroducing electronic-system electrodes to contact the gauged liquid.As a result the electric circuit is closed at certain liquid level andthe liquid level is determined on that basis.

Also known are the capacitive electronic sensors with frequencygenerator having a capacitor of capacitance depending on the surroundingenvironment, whereas the presence of this environment is detected bymeasuring the capacitance of the capacitor through checking thefrequency of the generator.

The liquid level indicator, known from the Polish patent application No.P-301505, contains an electronic unit and gauging tip, located in thelower part of the indicator body and contacting the sender and receiverof the electronic unit provided with contact set at its opposite side.

Also known from the Polish patent application No. P-327547, is themethod of measuring the velocity and/or volume of flowing dielectricsubstance, especially in form of liquid, wherein the stream ofdielectric substance is passed between capacitor plates of which oneplate is divided to two parts by a slot transversal to the flow of thedielectric substance, and then both plates are connected electricallythrough a resistance. A constant power-supply voltage is maintainedbetween capacitor plates and the voltage, and/or current flowing betweenparts of divided plate, is/are measured and then the velocity and/orvolume of flowing dielectric substance is determined from suitablerelationship.

Also known, from the Polish patent application No. P-349033, is thepiezoelectric device for measurement of liquid level containing adetector provided with two piezoelectric cells combined with controlelements for suitable emission of ultrasonic waves opposite a suitablereflective reference element located at a known distance from respectivecell on one part and the higher liquid surface on the other, theprocessing element being adapted to determine the level of liquid usingrespective propagation times of ultrasonic waves emitted by each ofthose two cells. This unit contains elements which, on voltage supply tothe unit, are able to determine the initiation phase (1100, 1100 bis),during which the control elements control the piezoelectric cells, sothat the ratio between the reference cell excitation rhythm andlevel-measurement-cell rhythm is higher compared to the respectiverhythms during the subsequent phase of stabilized measurement (1300).

The aim of this invention is to develop a method and electronic systemfor monitoring the level of liquids in containers of diverse usesthrough their electric insulation while simultaneously eliminating thecontact of those liquids with measuring element as in case of electrodesor floats.

The essence of the method of detecting the presence of conducting ordielectric environment with dielectric constant higher than that of airaccording to this invention consists in counting of the number ofreference control signals, which are a function of: electric chargescollected on the measuring capacitor during its charging, electriccharges collected on the reference capacitor during its charging withpulse control signal, power-supply voltage to the control unit that is asource of the current for charging the measuring and referencecapacitors, the control-system preset voltage to which the measuringcapacitor should discharge itself during counting of the referencecontrol signals and the ambient temperature of said measuring capacitorand said reference capacitor, said signal being sent from said controlsystem as necessary for charging of said measuring capacitor, and thenthe previously-charged measuring capacitor is discharged to a thresholdvoltage preset by said control system and, subsequently, the countingtakes place of the number of control signals that depend on surroundingenvironment and are a resulting function of: electric charges collectedon the measuring capacitor during its charging, electric chargescollected on the capacitor, which is dependable on the surroundingenvironment, during its charging with pulse control signal, power-supplyvoltage to the control unit that is a source of the current for chargingsaid measuring and reference capacitors, the control-system presetvoltage to which the measuring capacitor should discharge itself duringthe counting of reference control signals, and the ambient temperatureof the measuring capacitor and reference capacitor, said signals beingsent from control system as necessary for charging of the capacitordependable on the surrounding environment, and then thepreviously-charged measuring capacitor is discharged to the thresholdvoltage preset by said control system and, subsequently, a comparisontakes place of determined control signals with their reference state,and the thus-obtained difference in those signals indicates the presenceof conducting or dielectric environment that surrounds the capacitorinfluenced by this environment.

In turn, the electronic system for detecting the presence of conductingor dielectric environment with dielectric constant higher than that ofair, according to this invention, consists of microprocessor controlsystem having a measuring capacitor in its electric circuit, andelectrically connected with measuring sensor consisting of firstelectronic key and the capacitor dependable on the surrounding,conductive or dielectric, environment, connected with it, whereas thecontrol-system line, which constitutes the charging-current output ofthe capacitor dependable on the surrounding environment, as well as theinput of the measuring-capacitor discharging current, is connected withsaid key, whereas the line of said system, constituting the outputof/for the measuring-capacitor charging current as well as the input forvoltage testing during discharging of said capacitor, is connected withsaid capacitor and with said key, whereas the line of said system,constituting both the input of the measuring-capacitor charging currentand the output for the discharging current of said capacitor, isconnected through said capacitor with the first electronic key, whereasthe common of the control system is also connected with said key throughsaid capacitor dependable on the surrounding environment.

In its other embodiment the electronic system contains additionally areference sensor consisting of the second electronic key, connected withthe control-system line, constituting the output of the measuringcapacitor as well as the input for voltage testing during discharging ofsaid capacitor, and the reference capacitor connected with said key, onepole of said reference capacitor being connected with the common of saidsystem as well as, through the capacitor dependable on the surroundingenvironment, with said first electronic key, whereas the control-systemline, which constitutes the charging-current output of the referencecapacitor as well as the input of the measuring-capacitor dischargingcurrent, is connected with said second key of said electronic referencesensor.

The method and system of this invention enable easy and quick detectionof the presence of conducting or dielectric environment with dielectricconstant higher than that of air, whereas a simple housing case of thesystem enables its versatile applications, including householdsappliances, thermos-vessel outfit of gastronomic establishments and theautomotive industry, to measure fuel contents in fuel tanks.

The subject of the invention is described in more detail on itsembodiment examples of electronic systems for use of the method of thisinvention shown in figures, wherein FIG. 1 is a schematic block diagramof the electronic system for detection of the presence of conducting ordielectric environment with dielectric constant higher than that of air,consisting of a control system and measuring sensor, whereas FIG. 2 is aschematic block diagram of the electronic system for detection of thepresence of conducting or dielectric environment with dielectricconstant higher than that of air, consisting of control system,measuring sensor and reference sensor.

DETAILED DESCRIPTION

The electronic system presented in FIG. 1 consists of microprocessorcontrol system US, having the capacitor Cp, in its electric circuit, andelectrically connected with measuring sensor CP, consisting of theelectronic key K1, and the capacitor Cx dependable on the surrounding,conductive or dielectric, environment, connected with it, whereas theline Pn, of said control system US, constituting the charging-currentoutput of the capacitor Cx, as well as the discharging-current input ofthe capacitor Cp, is connected with key K1, whereas the line I/S of saidsystem, constituting the output of/for the charging current of thecapacitor Cp as well as the input for voltage testing during dischargingof the capacitor Cp, is connected with said capacitor and with key K1,whereas the line CEN of said system, constituting both the input of thecharging current of capacitor Cp and the output for the dischargingcurrent of said capacitor, is connected, through capacitor Cp, with keyK1, whereas the common of the control system US is connected with key K1through capacitor Cx.

The electronic system presented in FIG. 2 consists of microprocessorcontrol system US, having the capacitor Cp, in its electric circuit, andelectrically connected with the measuring sensor CP, consisting of theelectronic key K1, and the capacitor Cx dependable on the surrounding,conductive or dielectric, environment, connected with it, whereas theline Pn, of the control system US, constituting the charging-currentoutput of the capacitor Cx, as well as the discharging-current input ofthe capacitor Cp, is connected with key K1, whereas the line I/S of saidsystem, constituting the output of/for the charging current of thecapacitor Cp as well as the input for voltage testing during dischargingof the capacitor Cp, is connected with said capacitor and with the keyK1, whereas the line CEN of said system, constituting both the input ofthe charging current of capacitor Cp and the output for the dischargingcurrent of said capacitor, is connected, through capacitor Cp, with thekey K1, whereas the common (frame) of the control system US is connectedwith key K1 through capacitor Cx.

Also, this embodiment of the system is additionally provided with thereference sensor CO consisting of the electronic key K2, connected withthe line I/S of the control system US and to the reference capacitor Codconnected to said key, one pole of said reference capacitor beingconnected with the common of said system as well as, through thecapacitor Cx, with K1, whereas the line I/S of the control system US,which constitutes the charging-current output of the reference capacitorCod as well as the discharging-current input of the capacitor Cp, isconnected the electronic key K2 of the reference sensor CO.

The principle of operation of the electronic system of this invention isthat, once the supply voltage Ucc is switched ON in the control systemUS, electric charges Qp accumulate in capacitor Cp in the electriccircuit: the output I/S of the control system US and the input CEN, andthen the output I/S is switched over as the input for measuring of thevoltage on the capacitor Cp. Simultaneously, the electronic keys K1 andK2 remain inactive because of no signals in lines Pn and Pod of thecontrol system US.

Once the charging of capacitor Cp is finished, the electron key K1remains inactive, while the electronic key K2 becomes activated withcyclic rectangular signal No through the line Pod and said key K2 causesa switching enabling accumulation of charges Qod in the capacitor Cod,according to the relationship: Qod=f(Cod, Ucc, T), the source of whichis high level of control signal in the circuit: the output Pod of thecontrol system US, the electronic key K2, the capacitor Cod, and thecommon of the control system US.

After a specific time the low level of the control signal causes aswitching of the electronic key K2 to the discharge condition of thecapacitor Cp, according to the relationship Qr=f(Qp, Cod, Ucc, T) in thecircuit: the capacitor Cp, key K2, the line Pod of the control system USand the line CEN is such manner that the quantity of charges flowing offthe capacitor Cp depends on the quantity of charges collected in thecapacitor Cod during its charging. Such pulse-like discharge ofcapacitor causes a step-wise drop in the voltage on/in the capacitor Cp,which is monitored and compared by the control system US with the levelof the threshold voltage Up. The control system US sends so many controlsignals No depending on (Qp, Qod, Ucc, Up, T) until the voltage on thiscapacitor reaches the level of the threshold voltage Up preset on/by thecontrol system US, said signals being subject to counting and saving asNo.

Then the cycle is repeated from the re-collecting of charges in thecapacitor Cp in which the key K2 remains inactive and key K1 becomesactivated with cyclic rectangular signal Nx through the line Pn and saidkey K1 causes a switching enabling the accumulation of charges Qx in thecapacitor Cx, according to the relationship: Qx=f(Cx, Ucc, T), thesource of which is high level of control signal, whereas the quantity ofcollected charges depends on the environment surrounding the capacitorCx, in particular its dielectric constant in the circuit: the output Pnof the control system US, the electronic key K1, the capacitor Cx, andthe common of the control system US.

After a specific time the low level of the control signal causes aswitching of the electronic key K1 to the discharge condition of thecapacitor Cp according to the relationship Qr=f(Qp, Cx, Ucc, T) in thecircuit: the capacitor Cp, key K1, the line Pn of the control system USand the line CEN is such manner that the quantity of charges flowing offthe capacitor Cp depends on the quantity of charges Qx collected in thecapacitor Cx during its charging, thus causing a step-wise drop in thevoltage on/in the capacitor Cx, which is monitored and compared by thecontrol system US with the level of the threshold voltage Up. Thecontrol system US sends so many control signals Nx depending on (Qp, Qx,Ucc, Up, T) until the voltage on this capacitor reaches the level of thevoltage Up preset on/by the control system US.

Said signals are subject to simultaneous counting and saving as Nx, andthen a comparison takes place of the recorded quantity of controlsignals No and Nx and the results serves as the basis for the controlsystem US to signal the presence of conducting or dielectric environmentaround the capacitor Cx.

It is also possible to detect the conducting or dielectric environmentin the vicinity of the capacitor Cx in a single measuring cycle, i.e.without the use of the reference sensor CO, the key K2, and thecapacitor Cod.

However in this case the base reference is the counted quantity ofcontrol signals No necessary for discharging the capacitor Cp andcharging the capacitor Cx when air is the environment surrounding thecapacitor Cx. That quantity of signals No is saved and, after eachmeasuring cycle in which the presence of dielectric environment ischecked, it is compared with the quantity of counted signals Nx and onthis basis the control system US signals the presence of conducting ordielectric environment in the vicinity of the capacitor Cx.

1. The method of detecting the presence of a conducting or dielectricenvironment with dielectric constant higher than that of air with theuse of measuring sensor provided with capacitor wherein there's countingthe number of control signals (No), resulting from the relationshipNo=f(Qp, Qod, Ucc, Up, T), sent from the control system (US) asnecessary to charge the capacitor (Cp) and then to discharge thepreviously-charged capacitor (Cp) to a threshold voltage (Up) preset bysaid control system (US), with the subsequent counting of the number ofcontrol signals (Nx), resulting from the relationship Nx=f(Qp, Qx, Ucc,Up, T), sent from said control system (US) as necessary to charge thecapacitor (Cx) and then the previously-charged capacitor (Cp) isdischarged to said threshold voltage (Up) preset by the control system(US), where: Qp—means the electric charge(s) collected in capacitor Cpduring its charging Qod—means the electric charge(s) collected inreference capacitor Cod during its charging with control signal NoQx—means the electric charge(s) collected in reference capacitor Cx,dependable on the surrounding environment, during its charging withcontrol signal Nx Ucc—means the supply voltage to the control system USand the charging voltage of the capacitors Cp, Cx and Cod Up—means thevoltage set by the control system US to which the capacitor Cp should bedischarged while counting the control signals No and Nx T—means theambient temperature at which capacitors Cp and Cx and the remainingelement of the control system US are counting the discharge cycles ofcapacitor Cp with subsequent comparison of the number of determinedcontrol signals (Nx) with their reference state (No), and the obtaineddifference in those signals indicates the presence of a conductive ordielectric environment in the immediate environment of the capacitor(Cx).
 2. Electronic system for detection of the presence of a conductingor dielectric environment with dielectric constant higher than that ofair, having the measuring sensor with capacitor characteristics whereinit consists of the microprocessor control system (US) having in itselectrical circuit the capacitor (Cp) electrically connected with themeasuring sensor (CP) consisting of the electronic key (K1) and thecapacitor (Cx) dependable on the surrounding, conductive or dielectric,environment, connected to said key (K1), whereas the line (Pn) of thecontrol system (US), constituting the charging-current output of thecapacitor (Cx) as well as the discharge-current input of the capacitor(Cp), is connected with the key (K1), the line (I/S), constituting thecharging-current output of the capacitor (Cp) as well as the input forvoltage testing during discharging of the capacitor (Cp), is connectedwith said capacitor and with key (K1), whereas the line (CEN) of saidsystem, constituting both the charging-current input for capacitor (Cp)and discharge-current output of said capacitor, is also connectedthrough capacitor (Cp) with said key, whereas the common (frame) of thecontrol system (US) is connected through capacitor (Cx) with key (K1).3. Electronic system according to claim 2 wherein it has additionalreference sensor (CO) consisting of the electronic key (K2), connectedto the line (I/S) of the control system (US) and, connected with saidkey, the reference capacitor (Cod) with one pole connected to common ofsaid system and, through capacitor (Cx), to the key (K1), whereas theline (Pod) of the control system (US) constituting the charging-currentoutput of the reference capacitor (Cod) as well as the discharge-currentinput of the capacitor (Cp), is connected with the key (K2) of thereference sensor (CO).